Ukrainian government announced on Wednesday that it closed the country’s airspace to all Russian planes after Russia's oil giant Gazprom halted gas supplies to Ukraine.
Ukrainian Prime Minister Arseniy Yatsenyuk said at a televised government session that "The Ukrainian government has decided to ban all transit flights for all Russian airlines in Ukraine's airspace."
"The government is instructing [aviation authority] Ukraerorukh, in line with the norms of international law, to inform the Russian Federation that Russian airlines and Russian aircraft do not have the right to use Ukraine's airspace any longer."
Gazprom chief Alexei Miller said early on Wednesday that the state giant had cut off gas deliveries to Ukraine’s Naftogaz until the country makes upfront payment to Russia.
Following the recent debates over the gas deliveries, Moscow and Kiev had decided that Ukraine would make payment before receiving the gas.
Miller said Ukraine had received all gas it had paid for, Miller said in a statement, adding that ,"as such, deliveries have been stopped until the receipt of new payments from the Ukrainian company."
"The refusal to buy Russian gas will create serious risks for the reliable transit of gas to Europe through Ukraine and for the supply of gas to Ukrainian consumers during the upcoming winter," Miller added.
However Yatsenyuk denied the Russia’s claims, saying that Ukraine decided to stop buying gas from Gazprom because it saw better opportunities to supply it.
"The government has made the decision to order [Ukraine's national oil and gas company] Naftogaz to stop buying Russian gas."
"They got it all wrong. It is not them who are not supplying gas to us, it is us who are not buying gas from them. This is being done because offers that have come from our European partners - price offers - are much better than the offers from our eastern neighbour.”
The relations between two countries have remained tense since Moscow's annexation of Crimea in March 2014.
The dispute between two countries is worsening after blackouts in Crimea affected almost one million people since Tuesday.
The four electricity lines that provide Crimea with power from Ukraine were first attacked on Friday. Explosions damaged two lines and destroyed the other two.
The Russian government announced a state of emergency in Crimea on Sunday, after the electricity power lines from Ukraine were blown up.
After Russia’s announcement, Ukrainian authorities said that they would ban food imports from Russia and that this would cause damage to the reciprocal trade agreements between the two countries.
Despite Ukraine’s reservations, Russia continued its threats."Today or tomorrow gas deliveries will be stopped because of lack of advance payment," said Russian Energy Minister Alexander Novak to Vesti FM radio.
"There are different options, political ones, economic ones, Russia delivers coal to the Ukrainian energy sector. We could, and maybe in this situation we need to, take a decision about halting deliveries" he added.
But the Ukrainian government rejected all of Russia’s allegations about its inaction to rebuild power lines.
"This is an absolutely groundless assertion and the quick reaction of the government regarding repairs on the power lines and its guaranteeing of security for people in the emergency zone is proof of this," a Ukrainian official said in an email.